Expression And Purificaition Of The B Cell Receptor Complex

Humoral immunity is one of the most important parts of human adaptive immunity,and B cells play an irreplaceable role in it.The cell membrane surface of B cells expresses B cell receptor,which is an immune membrane protein receptor that can specifically recognize and bind antigens.The essence of BCR is membrane immunoglobulin,which is usually co-expressed with CD79A/B complex,a heterodimer molecule involved in signal transmission.And the total of this co-expression is called the BCR complex.The types of BCR are varied,among which Ig M and Ig D are expressed in the inactive initial B cells,but CD79A/B is always the same in the complex.With the development of membrane protein purification,crystallization and freezing electron microscopy,many common membrane protein receptors have been analyzed.So far,there have been few studies on the structure of the BCR complex,how to obtain BCR complex through in vitro expression and purification,whether the structure is just like the previous studies,and how does signal transduction between m Ig and CD79A/B work,these questions remain unresolved.In this study,expression and purification of λIg M-BCR complex and κIg D-BCR complex were performed through the mammalian cell expression system,the HEK293 F cell line.We used the purification method of membrane protein,and the high quality protein was obtained by fast protein liquid chromatography combined with molecular sieve.Since the protein content and quality obtained from the initial expression purification test were not high,the screening test of detergent was carried out and the vectors were modified to explore an appropriate expression purification method of BCR complex.Through the screening of 21 kinds of detergents,a suitable detergent L360 S was selected for λIg M-BCR complex.At the same time,the expression of CD79A/B was improved by the modification of the vector.At the end of the study,some new methods were used to express and purify κIg D-BCR complex,and good results were obtained.To sum up,the screening of detergents and the modification of carriers improved the expression and purification effects of BCR complex to some extent,laying a good foundation for the future analysis of its structure.